1. Field of the Invention
The present invention relates to asphaltic foams which are useful in roofing and in other applications.
2. Description of the Related Art
1. Asphaltic Foams
Many attempts have been made to incorporate asphalt into polyurethane foams. Primarily, asphalt has been used as a filler material for such foams, due to the fact that it is less expensive than the precursor chemicals used to produce polyurethane foam. For example, in Spanish Patent Application No. 375,769, a process is described in which asphalt powder is added to a polyurethane precursor mixture as a filler material. The asphalt powder and polyurethane form a uniformly distributed plastic mass.
The addition of asphalt to a polyurethane foam can also, however, impart certain desired characteristics to the foam. In Japanese Patent Application No. 76/64,489, for example, a polyurethane foam was waterproofed through the addition of asphalt to the polyurethane precursors. Another asphalt-polyurethane mixture having good sound absorption and anti-vibration properties is disclosed in Japanese Patent Application No. 77/68,125.
Most prior art processes for incorporating asphalt into polyurethane, such as Japanese Patent Application No. 76/64,489, have made use of soft asphalts with low softening points. Such asphalts can be liquified and blended with polyols at relatively low temperatures to form a uniform, liquid mixture of asphalt and polyols. By completely blending the liquified asphalt with the polyols, a uniform asphalt-polyurethane foam product can then be produced. In addition, because low softening point asphalt remains liquid at relatively low temperatures, the asphalt-polyol mixture can be reacted to form a foam at temperatures which are low enough that a controlled reaction can take place. However, such foam products generally have a relatively low asphalt content.
In Japanese Patent Application No. 76/64,489, for example, a soft asphalt having a needle penetration degree of 80 to 100 is used. This asphalt has a correspondingly low softening point of under 150°. In the process of this patent, the asphalt is mixed with polyurethane precursors, and this mixture is then reacted to form a compressible product, i.e. a soft foam.
The use of such soft asphalts in prior art processes is acceptable when it is desirable for the resulting product to be a soft foam. However, in certain applications, a rigid asphaltic polyurethane foam would be advantageous. A process for making a rigid asphaltic polyurethane foam is disclosed, for example, in U.S. Pat. No. 4,225,678 to Roy. In this process, relatively high molar ratios of isocyanate to polyols are recommended, in some cases as high as 11:1. The Roy process therefore resulted in products which were too friable and/or which lacked sufficient compressive strength. When conventional roofing asphalt having a softening point of over 200° F. was used in the Roy process to produce asphaltic foams, the foaming reaction also was too fast, making manufacturing of asphaltic foams impracticable.
In U.S. Pat. Nos. 5,786,085; 5,813,176; 5,816,014; and 5,965,626 all to Tzeng et al., all herein incorporated by reference, an asphaltic foam useful in roofing applications is disclosed.
2. Asphalt in the Roofing Industry
Various asphalt-coated or asphalt-impregnated materials are in common use in the roofing industry. For example, water absorbent paper which has been saturated with low softening point asphalt, known as saturated felt, is usually placed underneath other roofing components. The asphalt of the saturated felt provides the felt with secondary water repellency.
Higher softening point asphalt is put on either side of saturated felt to form base sheets, which go under the tiles of a roof to build up the roof system. Base sheets with mineral surfacing on their upper surfaces, known as mineral surface rolls, provide enhanced durability and fire retardancy to a roof and can also enhance a roofs appearance. Mineral surface rolls have been used as ridge caps, the largely ornamental structures which straddle the peak of a roof.
However, asphalt-impregnated papers suffer from various drawbacks. When used as ridge caps, for example, mineral surface rolls must be bent to fit the ridge-line of a roof. Mineral surface rolls are also sometimes bent to make them thicker and give a ridge-line a layered appearance. Bending a mineral surface roll causes the asphalt and substrate to crack, however, leaving the cracked material exposed to the elements. The mineral surface roll tends to deteriorate at the site of such cracks within 3 to 4 years of being installed or even sooner, resulting in leaks and other roof damage.
Alternative materials, such as rubberized asphalt with a flexible polyester substrate, have also been used in the roofing industry. For example, modified asphalt has been used in mineral rolls to avoid cracking the asphalt and its substrate.
3. Polyurethane Foam in Shingles and Ridge Caps
One method for combining a polyurethane foam and an asphaltic material in roofing applications is suggested in U.S. Pat. Nos. 5,232,530 and 5,305,569 to Malmquist, et al. These patents teach that a polyurethane foam can be attached to the underside of an asphaltic material in order to produce a roofing shingle. Of course, this involves the manufacturing step of physically attaching the foam to the asphaltic material or otherwise forming the foam on the asphaltic material. The polyurethane foam and asphaltic material layers can, in addition, become delaminated.